2007 Fiscal Year Final Research Report Summary
Fluid distribution around a seismogenic zone along a plate boundary fault imaged and monitored by controlled source electromagnetic sounding
| Project/Area Number |
17340134
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Japan Agency for Marine-Earth Science and Technology |
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Principal Investigator |
GOTO Tada-nori Japan Agency for Marine-Earth Science and Technology, Institute For Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Technical Scientist (90303685)
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| Co-Investigator(Kenkyū-buntansha) |
KASAYA Takafumi Institute For Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Technical Scientist (90373456)
ARAKI Eiichiro Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, Technical Scientist (60359130)
ASAKAWA Kenichi Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, Group Leader (40344288)
SAYANAGI Keizo Institute of Oceanic Research and Development, Tokai University, 海洋研究所, Associate Professor (40332308)
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| Project Period (FY) |
2005 – 2007
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| Keywords | CSEM sounding / conductivity structure / OBEM / OBS / submarine cable / marine EM survey / seafloor observation / Tokai region |
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| Research Abstract |
In FY 2005, we carried out three feasibility studies and tests for long term monitoring of seimogenic zone. A numerical calculation codes for marine controlled source electromagnetic survey was developed. Marine DC resistivity surveys were conducted at two research cruises. Seismic records of aftershocks of the Sumatra great earthquakes were analyzed. These studies are helpful for new development and refinement of cabled long-term ocean bottom electromagnetometers and ocean bottom seismometers. In FY 2006, underwater tests for these ocean bottom instruments were carried out in a small pool. Also, the off-Toyohashi cable, located on the Tokai mega-earthquake zone, was pulled up by using a cable ship and was deployed after attaching a junction unit to the end. In FY 2007, the newly developed ocean bottom instruments were connected to the junction unit at the end of off Toyohashi cable. The JAMSTEC vessels and a ROV were used for the seafloor operations. As a result, a multidisciplinary c
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abled observatory, whose targets are submarine earthquakes, crustal deformation and groundwater flow below the seafloor, was constructed off-Toyohashi, just on the Tokai mega-earthquake zone. Continuous artificial electric signals are sent from the off-Toyohashi cable simultaneously, so that the first ocean bottom monitoring of electrical conductivity variation below the seafloor was started.
Before the continuous seafloor monitoring, marine magnetotelluric surveys were carried out off-Toyohashi area to image the crustal electrical conductivity structure around the Tokai mega-earthquake zone. Twelve instruments were deployed and recovered successfully. The obtained data set show us the conductivity structure of subducting Philippine Sea plate.
As a result, several papers and presentations were presented through this project, relating to the cabled observatory, marine controlled source electromagnetic survey and electromagnetic phenomena possibly excited by groundwater flow below the seafloor. Less
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